Bring a large pot of water to a boil over medium heat, then salt the water. Add the pasta and cook for 3 to 4 minutes, (it will be undercooked). Cool, drain well and add it to a large bowl.
Meanwhile, in a medium saucepan, heat 2 tablespoons of extra-virgin olive oil, 2 turns of the pan, and 1 tablespoon of the butter over medium to medium-high heat. Add the celery, onion, red pepper, garlic, bay leaf, thyme, lemon zest, salt and pepper, to taste. Cook to tender, 6 to 8 minutes. Add the crabmeat to the vegetables and season liberally with seafood seasoning. Stir to combine, then remove from heat.
In a medium sauce pot, over low heat, melt 3 tablespoons butter and whisk in the flour. Cook for 1 minute, then whisk in the milk and bring to a bubble. Season the sauce with salt, pepper and nutmeg, to taste, and cook for a few minutes, until the mixture coats the back of a spoon. Add the mustard and the cheese and stir in a figure 8 motion. Add the vegetables and crab, sauce to the bowl with the pasta and transfer the mixture to individual baking crocks or a large casserole dish. This can be made ahead to this point and refrigerated.
Preheat the oven to 375 degrees F.
To complete the dish, melt a couple of tablespoons butter in a small skillet, over low heat and add 3 tablespoons hot sauce. Warm through, then add the panko crumbs and toss to evenly coat the crumbs in sauce mixture. Cool the crumbs, then toss in the parsley and 1/2 cup grated Parmigiano -Reggiano cheese. Top the mac n cheese with the spicy crumb mixture. Arrange individual crocks on a baking sheet or put the casserole on baking sheet to catch any drips. Bake until brown and heated through, about 10 minutes. If cooking from cold, the mac n cheese will take 40 to 45 minutes, but add the crumbs the last 10 minutes of baking.
Recipe courtesy of Rachael Ray